Amplifying system



April 22 1 924 4 5 39 H. C. THOMPSON AMPLIFYING SYSTEM Filed F eb. 2a. 1921 l i l m m l i ,1 7

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fatented Apr. 22, 1924i.

tar, career @Fl EARRY G. THOMPSON. OF SCHENECTADY, NEW YORK. ASSIGNOR TO. GENERAL ELEC- RH? CQMPANY, A CORPORATION OF NE'W YORK.

AMFLIFYING SYSTEM.

Application filed February 26, 1921.

To a l 1 37mm it may concern.

B it known that l, linear C. 'l'nonrson, a citizen of the l'nited States. residing'at Schenectady. county of Schenectady, State of New York. have invented certain new and useful improvements in Amplifying Systems, of which the following is a specification.

My present invention relates to amplifyinc" systems, and more particularly to systems employing electron discharge devices of the dynatron or negative resistance type.

In the operation of such devices in the past it has been customary to supply the electrical variations to he amplified directly to the negative resistance circuit and thereby vary the potential o the secondary cathode with respect to the primary cathode, at the same time maintainin the anode potential constant. The amplifying action takes place entirely in the negative resistance circuit and the amplified variations are either utilized in this circuit or supplied either y direct or inductive.coupling to other circuits. One of the disadvantages arising from this method of operation lies in the fact that in order to utilize this circuit as both the input and output circuit. some inductance must. be included in the circuit 0 and under these circumstances the circuit has an inherent tendency to oscillate by reason of its negative resistance characteristic.

The object of my present invention is to provide a circuit. arrangement which will malre use of the negative resistance characteristio of such devices for amplification, and in which the input and output circuits will be entirely stable in their operation.

The novel features which I believe to be characteristic of my invention are setforth with particularity in the appended claims, my invention itself, however, both as to its organization and method of operation togather with further objects and advantages thereof will best be understood by reference to the following description talren in connection with the accompanying drawing in which Figs. 1 and 2- illustrate diagrammatically two ditierent circuit arrangements which may be employed in carrying my invent on into effect.

As indicated in Fig. 1, l employ an electron discharge device 1. having the usual filamentary cathode 2 adapted to be heated to incandescence by means of current de- Serial No. 447,971.

rived from the source 3, a grid electrode a and a third plate electrode 5 surrounding the cathode and grid electrode. A battery (3 or other convenient source of direct current may be employed for impressing a positivc potential upon the grid electrode 4: and

a second source 7 for impressing a positive potential upon the plate elect-rode 5 with respect to the cathode The potential of the plate electrode 5 in this instance is higher than that of the grid electrode d and these potentials are so chosen that the plate electrode 5 acts as anode and the grid electrode 4 acts as secondary cathode.

In the usual operation of such devices in th past the variations to be amplified have been impressed upon a circuit between the primary cathode and the secondary cathode so as to vary the potential of the secondary athode with respect to the primary cathode, the potential of the anode remaining constant with respect to the primary cathode. This arrangement hasthe disadvantages mentioned above and to overcome this disadvantage l impress the variations ,to be amplified upon the system in such a way that the potential of the primary cathode is varied with respect to both the secondary cathode and the anode. This is accomplished by impressing the electrical variations to he amplified upon the system by means of the transformer 8, the secondary of which is common to the circuit between primary cathode and anode and the circuit between primary I cathode and secondary cathode.

Y rtssuminc that the potentials of the two electrodes 4 and 5 are fixed by means of the batteries 6 and 7, the potential of the primary cathode 2 with respect to electrodes 4 and 5 will vary in accordance with potential variations produced in the secondary of transformer 8. This will produce variations in the current to electrode 4- by reason of the negative resistance characteristic of the system and equal and opposite variations in the current to electrode 5. The current in the which I have described.

The negative resistance of the device may be balanced by means of a positive resistance 9 so that small variations in the potential of the primary cathode with respect to the secondary cathode will produce large variations in current flowing between primary cathode and secondary cathode. in order to eliminate the necessity of inserting inductive device in any portion of the circuit which has a negative resistance characteristic, potential variations setup across resistance 9 may be impressed upon the grid circuit or". an electron discharge amplifier 1O the telephone receiver 11 in the plate cirM-it of this amplifier will give an indication of the amplified variations if these hapto be audible frequency. if the vari as to be ampl fied are of radio frequency the device 10 may also act as a detector. a variable condenser 12 may be shunt to the secondary of transor tuning the input to the varia- 1 are to be amplified.

have shown a circuit arrangewhich is similar in its manner of opn to that shown in Fig. 1, the main cc however being that the function of the electrodes 4 and 5 is interchanged. In this case the electrode 5 acts as a secondary cathode and the electrode as the anode. Since the current variations in the negative resistance circuit produce corresponding equal and opposite variations in the circuit flowing in the anode circuit, the telephone receiver 11 may be inserted in the anode circuit as indicated.

-ffhile I have shown and described the preferred embodiments of my invention, it will be understood that my invention is by no means limited to the particular circuit arrangements shown as many variations in the electrical connections employed as Well as in the form of apparatus used may be made without departing from the scope or" my invention as set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. An amplifying system comprising an electron discharge device having an electron emitting cathode, an anode and a third elecd1 we e trode enclosed in an evacuated receptacle,

sources of potential applied to said electrodes in such a way that the device has a working range over which the current flow from the cathode to the third electrode varies inversely as the potential applied thereto and means for varying the potential of the cathode with respect to both the anode and third electrode in accordance with the electrical variations which are to be amplified.

2. An amplifying system comprising an electron discharge device having an electron emitting cathode, an anode and a third electrode enclosed in an evacuated receptacle, sources of potential applied to said electrodes in such a way that the device has a working range over which the current flow from the cathode to the third electrode Vitries inversely as the potential applied thereto, a circuit between cathode and anode, a circuit between cathode and third electrode and means common to both of said circuits for supplying to the system electrical variations which are to be amplified.

3. An amplifying system comprising an electron discharge device having an electron emitting cathode, an anode and a third electrode which is interposed between cathode and anode, sources of potential applied to said electrodes in such a way that the device has a working range over which the current flow from the cathode to the third electrode varies inversely as the potential applied ing the potential of the cathode with respect to both the anode and third electrode in accordance with the electrical variations which are to be amplified.

4. An amplifying system comprising an electron discharge device having an electron emitting cathode, an anode and a third electrode which is interposed between cathode and anode, sources of potential applied to said electrodes in such a Way that the device has a working range over which the current flow from the cathode to the third electrode varies inversely as the potential applied thereto, a circuit between cathode and anode, a circuit between cathode and third electrode, and means common to both of said circuits for supplying to the system electrical variations which are to be amplified.

5. An amplifying system comprising an electron discharge device having an electron emitting cathode, an anode and a third electrode, circuit connections between the different electrodes, sources of potential included in said circuit connections of such values that the current flow in a portion of said circuit connections over a predetermined range of applied potential varies inversely as the applied potential, and means for impressing'potential variations upon a portion of the circuit connections'in which the current flow is independent of the applied potential.

thereto and means for vary- 6. An amplifying system comprising an electron discharge device having an electron emitting cathode, an anode and a third electrode, circuit connections between the different electrodes, sources of potential included in said circuit connections in such a way that in a portion of the circuit connections the current tlow over a predetermined range of applied potential varies inversely as the applied potential, and means for impressing potential variations upon another portion of the circuit connections and thereby varying the potential relations between the electrodes.

7. An amplifying system comprising an electron discharge device having an electron emitting cathode, an anode and a third electrode, circuit connections between the difierent "electrodes, sources of potential included in said circuit connections in such a Way that in a portion of the circuit connections the current flow over a predetermined range of applied potential varies inversely as the applied potential and means for impressing potential variations upon another portion of the circuit connections and thereby varying the potential relations between the electrodes and producing corresponding but amplified potential variations in that portion of the circuit connections in which the current varies inversely as the applied potential.

In Witness whereof, I have hereunto set my hand this 25th day of February, 1921. HARRY C. THOMPSON. 

